Selection and Identification of Interwell Tracers for Reservoir Characterization of Clastic Rock: A Case Study from Cretaceous Himmatnagar Sandstones

Tracer technique is being used globally in oil field reservoir under different stages of production. The methodology is immenselyimportantto understand the reservoir complexity during pressure maintenance by water/ gas injection and in EOR applications. Therock-fluid interaction andlocal velocity of the injected fluid in the reservoir are controlled by various parameters such as types of rock, grain size, and pore size distribution and their interconnectivity, types of minerals distributions and their interaction with the local fluids under in-situ conditions of the reservoir. However, the fluid flow dynamics is also controlled locally by capillary and viscous forces acting at the interface between the two immiscible fluids at contact, Interfacial Tension (IFT), wetting and non-wetting phase saturation distributions, a variation of rock facies and heterogeneity variation distribution. It is also impacted by the compositionofoil, water and gas and theproduction and injection scenarios of the reservoir. Therefore, to understand the local velocity of the injected fluid, an inert chemical/ or radioactive tracers are tagged with the injection fluid. These tracers follow the same track in the reservoir as the injected fluid moves locally, subject to the chemical species are thermally stable and compatible with reservoir rock matrix and formation fluids. To see this different aspect chemicals such as Pot. Iodide (KI), Ammo. Thiocyanate, Picric, and Boric acid have been studied for thermal stability, adsorption/ desorption of these chemicals as a tracer on reservoir rock matrix and their constant dispersion estimation at reservoir temperature (~1000C) on Himmatnagar Sandstones. The XRD studies of the rock matrix alsoconfirmed mainly 84.28% Quartz with fraction of Kaolinite and Illite composition. However, from the above four tracers Ammonium Thiocyanate, Boric acid, and Picric acids are the best tracers which show the value of dispersion constant of the order of 0.5cm/sec to 1.2 cm/sec at Lab. scale respectively. However, KI was not found suitable for clastic rock due to some compatibility problem. The studies also reflect that a dose of the 200ppmconcentration of tracer seemed to be optimumand to be tagged with injected fluid for better reservoir characterization and effective reservoir management for ultimate oil gain.